Precise Measurement of Pion Cross-section*Motoyasu Ikeda for PIAνO-Hparpsichord collaboration *Kyoto Univ.

1. Motivation : Why Pion interaction ?
For neutrino experiment:
If a secondary π generated by neutrinoνinteraction is absorbed by nuclei, such π
is not detected. This becomes major
backgrounds for νe appearance, and theenergy spectrum of CCQE ν events wouldp
be distorted. Thus, precise measurements
primaryof π interaction is necessary for thenucleon
precise measurement of the oscillation
parameters.
For nucleon decay experiment:
π interaction also plays a key role tonucleon decay. This is because that for Kν
mode, most Ks are detected via K+→π+π0
channel. Also our result is very useful toevaluate the MC simulation of e π0 mode,and could determine how much fraction ofthe π0 should interact in the nucleus.

Before track reconstruction is implemented, we needed to verify our data.
Also, the result of this study will be compared with the result with trackreconstruction, and check the systematic uncertainty on both results.

e/μπpν

4. Hit level analysis

Scattering?
Absorption?
Charge Ex?

Selection of Absorption/Cx candidate

secondarynucleon

if the particle is mip or not without track reconstruction,
since the angle of the track is not clear.
Nx= #of large hit in X’
Nx –Ny-0.25< Nx+Ny <0.25 Ny= #of large hit in Y’

π+K

π0pe+

π0

1 Incoming mip particle should be in inside 20 fiber (out of 32)
2 Clean event selection
These large charge hits (red circles) are difficult to say
X’ view

3 Number of layers which incoming mip particle went straight: 3<Nlayer<13Red:4 Total PE > 600 p.e. (mip hit ~12p.e.)Abs like
5 Total PE of mip range hit/#of large hits(Rmip<25)
Black:
Absorption likeπ+How muchcharge ex?

X’ view
subtracted

22m

Y’ view
subtracted

subtracted

Y’ view

X’ view
RmiprejectRed:
Abs/Cx likew/o total pe cut
Black: Nlay=15

M11 Beam line

V1

S2

V2

beam line

We took data with 2 configurations
B.

Harpsichord:
Miniature of T2K FGD
consists of 1cm
square scintillator
with WLS coupled toMPPC.
15layers of 32(x)×32(y) channels

PIAνOin Conf.A, Harpsichord has~1.5mm lead plates
in between each layer.

3. PIAνO detector

110cm

110cm

NaI charge [count]>Fraction of selected events andpenetrated events as a function ofPreliminary
incoming π momentum (right plot).
※ Selection/Detection efficiency
is not corrected.
(Need MC simulation)※ Fraction of π in each momentum
setting is corrected by fitting tof
distributions.
(Need to develop better method
using Cherenkov detector)※ After the robust selection cuts,
Beam momentum [MeV]
the statistical uncertainty is ~5%for Cx like events. Cf.
Past exp. data have >20% uncertainty.
>Next things to do- Use Harpsichord data to see Cx event
Data from past experiments- MC development
・MC based on G4・Implement NEUT π interaction into G4 code
・Develop PIAνO-Harpsichord integrated MC- Efficiency check for the hit-level analysis- Track reconstruction and Analysis- Get cross section- Systematic uncertainty study- Analysis of number of ejected nucleon after
absorption which is not simulated in current NEUT.
- Prepare for next beam test in May/Jun 2011
・Install water layer

DAQ board

8×8 fib. coupled
to 1 MAPMT

6. Summary
MAPMT iscoupled to FEB

Main volume of thedetector is 1.5mm×32
cubic =(48)3mm3Rmip

Cx like

5. Status and TO DO

S1A.

Total pe [p.e.]

Red:
Abs/Cx like
Abs/Cx w/o NaI cut
likeBlack: Nlay=15

Fraction

S0

Red:
Abs/Cx like
w/o Rmip cut
Black: Nlay=15

rejectNlayerChselected byeye scan ofevent display

subtracted

Red:
Abs/Cx like
Black: allend cap

reject Scatt like

Example of distributions for 250 MeV/c mode

TRIUMF Acc.

1.5 mm square×60cm length
scinti. fib.
16layers of32(x’) ×32(y’) :1024fib in total.

Inel. scattering like

6 NaI charge < 500 count

2. Experimental setup

Oct1/2010-Nov30/2010>480MeV/c proton from cycl.
>π+/π- beam at M11>Pπ: 150-375MeV/c>Trig rate(S0&S1): <30Hz>Config A: More eff. for Cx
Config B: Angular dist. of π0Y’ view

To measure absorption
and charge exchange
cross-section separately,NaI (crystal size :5cm×5cm×15cm)
detectors are installed todetect γs from π0 decays. Beam line
15NaIs for Config.A
16NaIs16NaIs for Config.B

15cm5cmfor Config.B to measure
angular dist. of π0 γs5cm>Precise measurements of π interaction are necessary for the precise
measurement of the oscillation parameters since the uncertainty of pion
interaction is one of major sources of systematic uncertainty for neutrino
beam flux and spectrum measurement.
>This measurement also contribute verification of MC simulation tonucleon decay experiment.
>From Oct.1 to Nov.30, 2010, we performed an experiment to measure
the pion interaction cross section at TRIUMF M11 beam line.
>For the experiment , two new detectors are developed: one in Kyoto andthe other one in TRIUMF.
>Hit level analysis is performed to check data quality. Even after the strict
cuts, we still have enough statistics (statistical uncertainty ~5%)
> We will summarize the result within 1year including the result from next
beam time from May 2011.